Mechanical resonator



Sept. 9, 1969 M. HETZEL EITAL 3,466,475

MECHANICAL RESONATOR Filed March 13, 1968 irvwvrv/es n m H TZEL REHY SEIGNEU-K Ma w B7 mTvfiA/lys United States Patent US. Cl. 310-25 10 Claims ABSTRACT OF THE DISCLOSURE A mechanical resonator having two arms oscillating in phase opposition and at least one compensating device including a cavity formed in a port integral with one of the arms and at least one mass placed freely in the cavity to at least partially and automatically compensate the variations of the frequency proper of the resonator due to changes of its orientation in space.

The present invention concerns a mechanical resonator of the type comprising two branches oscillating in phase opposition.

It is known that resonators of this kind, which are used for instance in watches, have the disadvantage of being affected with an error, the so-called error of position, which consists in that their frequency of oscillation proper is not invariable but on the contrary varies in dependence on the orientation of the resonator in space, in relation to the direction of gravity. The result is, for a wristwatch for instance, that the changes in orientation of the watch in relation to the vertical direction, necessarily entail an appreciable daily running error.

The purpose of the invention is to eliminate this defect and, to that end, the resonator according to the invention is characterized in that it comprises at least one compensating device comprising a cavity formed in a part integral with one of the said branches, and at least one mass placed in this cavity so as to move freely within it and thus compensate at least partially and automatically the variations of the frequency proper of the resonator due to changes of its orientation in space.

The appended drawing illustrates, by way of examples, an embodiment and variants of the resonator according to the invention.

FIGURE 1 is a plan view of a resonator provided with a compensator device in one of its two arms.

FIGURE 2 is an enlarged view in greater detail, in cross-section along 22 in FIGURE 1.

FIGURE 3 shows a view similar to that of FIGURE 2, but relating to a variant.

FIGURES 4 and 5 relate to another variant.

FIGURES 6 and 7 are partial plan views showing two ways of utilizing the device according to FIGURES 4 and 5 in the case of the resonator according to FIGURE 1.

The resonator (FIGURE 1) is formed by a metallic part, comprising two branches 1, 2, which are arched and symmetrical, joined by a middle part 3 by means of which the resonator is secured by screwing on a support which may be the body of a watch. The screws 4 secure the resonator to the associated device.

The branches 1, 2 are provided to oscillate in phase opposition and each of them comprises, at its free end, a mass 5 and 6, respectively belonging to an electromagnetic transducer of a known type ensuring the maintenance of the vibrations of the resonator. The location of the coil of the transducer is simply indicated in 7 and it is wellknown that it acts magnetically on the masses 5, 6 in order to ensure in conjunction with the elasticity of the branches 1, 2, the periodic motion of these masses towards and away from one another. The said arms are made thinner at 8, 9 in order to facilitate flexion at this point. Openings 10 are provided in the arms to make them lighter.

Member 11 serves for the fine adjustment of the frequency proper of the resonator, and is constituted in a known manner by a rotary eccentric member. The frequency proper of the oscillations varies slightly with the angular position of this member 11.

The straight line X-X, in dots and dashes, indicates the direction of the oscillating motion of the masses 5, 6.

In view of reducing, or better still, completely suppressing the error of position of the resonator according to FIGURE 1, the following means are provided.

In the same manner as the branch 2 is provided with a member for the fine adjustment of the frequency, the branch 1 comprises a chamber 12 destined to received an automatic compensating device of the error of position. In this exampe 11 and 12 are arranged symmetrically. In another embodiment, the compensating device could be placed elsewhere than in 12, and one could be provided on each of the arms. In another case, two members 11 could be arranged symmetrically, one on each arm.

Whereas it is true that a resonator comprising two compensating devices will have better operation than a resonator having only one compensating device, it is nevertheless clear that a resonator having only one compensating device will be better than one having no compensating device at all. If there is only one compensating device present, there will be some reaction in the middle part 3, but the force of this reaction is not suflicient to substantially disturb the resonator.

FIGURE 2 shows a larger scale view of the compensating device. The latter comprises a cylindrical metallic casing 13 hermetically closed by a stopper lid '14 forced into the casing, and the sealing may be completed by bonding, by means of Araldite for instance, the stopper lid on the casing.

A ball 16 is lodged within the cylindrical chamber 15 of the casing. The dimensions are chosen in such a manner that, as may be seen in FIGURE 2, there is only a very slight clearance between the ball, on the one hand, and the side wall, the bottom and the lid on the other. The ball is entirely free within the chamber 15, and the later is preferably filled, in the part which is not occupied by the ball, by viscous fluid which damps the movements of the ball.

The ball 16 is pierced by a diametrical bore 17 into one end of which is driven a mass 18 of high density metal, gold for instance, constituting for this ball an eccentric ballast which constantly tends, i.e. for any orientation of the resonator in space, to occupy the lowest possible position, beneath the geometric center of the ball.

The casing 13 is driven into the chamber 12 of the arm 1. The ball 16 may be made of a material such as ruby or sapphire, in order to reduce as far as possible the friction against the walls of the chamber 15.

The mass of the ball and that of its ballast will be calculated in such a fashion that the position error of the resonator is compensated as exactly as possible.

The chamber formed in the casing always has a revolution shape, whether it is cylindrical, as in FIGURE 2, or spherical or the shape of two cones.

It is known that in the case of a resonator according to FIGURE 1, the frequency proper is a minimum when the plane of this resonator is vertical, with the masses 5, 6 above and the middle part 3 below. This frequency is a maximum when the plane of this resonator is still vertical, but with the masses 5, 6 below and the part 3 above. For other orientations, the frequency proper lies between these two extreme values.

As for the compensating device, owing to the ballast 18 always taking up the lowest possible position, it may be seen that the center of gravity (eccentric) of the ball 16 and ballast 18 assembly is situated at a greater or lesser distance from the securing points 4, according to the orientation of the resonator in space. This automatic modification of the distance produces a change in the frequency proper of the resonator which is the reverse of that due to the position error mentioned above. By correctly dimensioning the ball and its ballast, the exact compensation of this position error is obtained.

In the variant according to FIGURE 3, the weighted ball 16, 18 is replaced by a ball 19 truncated at 20, i.e. of which a segment has been cut off, so that the center of gravity is eccentric.

FIGURES 4 and 5 illustrate, in axial cross-section and in plane view, respectively, another embodiment of the compensating device, which comprises a cylindrical metallic member formed by two parts 21, 22 dovetailed together and within which is formed a chamber in the shape of two opposed cones 23, 24 having a common base and arranged coaxially. In this chamber is freely disposed a ball 26, which under the influence of gravity, always comes to rest in the lowest possible position in the chamber 23,,24 whatever the orientation of the resonator may be in relation to the vertical direction.

The automatic compensation takes place when the device according to FIGURES 4, 5 is fitted in the chamber 12, either as indicated in FIGURE 6, or as indicated in FIGURE 7. In the case of FIGURE 6, the common axis 25 of the cones 23, 24 is parallel to the direction XX of the motion of the masses terminating the arms. In the case of FIGURE 7, this axis is perpendicular to the direction XX.

In another variant, which has not been shown, the compensating device could consist in a spherical chamber in which a ball of sensibly smaller diameter would be placed. The operation would be the same as that already described.

We claim:

1. Mechanical resonator comprising two arms oscillating in phase opposition, at least one compensating device including a cavity formed in a part integral with one of the said arms, and at least one mass placed in this cavity so as to move freely within it and thus compensate at least partially and automatically the variations of the frequency proper of the resonator due to changes of its orientation in space.

2. Resonator according to claim 1, wherein said mass is placed in a viscous medium filling the cavity.

3. Resonator according to claim 1, wherein said mass is of exteriorly spherical shape and comprises a ballast, so that the center of gravity of the assembly may be eccentric.

4. Resonator according to claim 1, wherein said mass is a sphere of which a segment has been removed.

5. Resonator according to claim 1, wherein said mass is of spherical shape with an eccentric center of gravity, the mass being disposed within the cavity with a clearance which is just sulficient to allow the free rotation in all directions of this mass above the center of its spherical exterior surface.

6. Resonator according to claim 1, wherein said mass has dimensions sensibly inferior to those of the cavity, in order that it may not only rotate about itself, but may also move freely in this cavity.

7. Resonator according to claim 6, wherein said cavity has a revolution shape.

8. Resonator according to claim 7, wherein said cavity is in the shape of two opposed cones with a common base and the common axis of which is parallel to the direction of the motion of oscillation at the point where this cavity is situated.

9. Resonator according to claim 7, wherein said cavity is in the shape of two opposed cones with a common base and the common axis of which is perpendicular to the direction of the motion of oscillation at the point where this cavity is situated.

10. Resonator according to claim 7, wherein said cavity is spherical.

References Cited UNITED STATES PATENTS 2,433,160 12/1947 Rusler 58-23 3,283,495 11/1966 Hetzel et al. 5823 2,806,400 9/1957 Grib 5823 3,146,582 9/1964 Lovetar 58-140 2,847,587 8/1958 Brasseur 3l019 MILTON O. HIRSHFIELD, Primary Examiner B. A. REYNOLDS, Assistant Examiner US. Cl. X.R. 

